N, n&#39;-alkylenecyanine dyes



Patented Feb. 13, 1951 N,N'-ALKYLENECYANINE DYES Leslie G. S. Brookerand Robert H. Sprague, Rochester, N. Y., assignors to Eastman KodakCompany, Rochester, N. Y., a corporation of New Jersey No DrawingOriginal application November 11,

1944, Serial No. 563,086. Divided and this application February 1'7,1949, Serial No. 77,055

11 Claims.

This invention relates to N,N'-allgylenecyanine dyes and to a processfor the preparation thereof.

It is known that N,N"-methyleneand N,N'- ethylene cyanine dyes can beprepared by condensing di-Z-quinolylmethane with methylene iodide orethylene bromide, and treating the resuiting condensation produce withpyridine or alkali [Scheibe and Fischer, Ber. 59, 502 (1926) We have nowfound that these known 2,2- cyam'ne dyes, as well as heretofore unknownN,N alkylenecyanine dyes which are not obtainable by the method ofScheibe and Fischer, can be prepared by condensing adi-2-.quinolylmethane, a di-2-benzothiazolylmethane, adi-V2-benzoxazolylmethane or other bis heterocyclic base derivatives ofmethane with an alkylene arylsulfonate. Our new process gives higheryields than the process of Scheibe and Fischer (in some cases very muchhigher), in addition to providing a means for obtainingN,N-alkylenecyanine dyes which could not be obtained by the priorprocess.

It is, accordingly, an object of our invention to provide new N,N'-alkylenecyanine dyes. A

Di-Z-benzothiazolylmethane zoo-240.7)

further object is to provide a processfor the preparationof such dyes.Other objects will appear hereinafter.

The N,N'-alkylenecyanine dyes can be prepared, in accordance with ouinvention, byreacting with an alkylene salt of the following generalformula:

wherein n represents a positive integer of from 2 to 3, and X and X eachrepresents an aryl sulfonate radical, upon a heterocyclic basederivative of methane of the following general formula: /Z\ I'Z/\ 1 'Iwherein Z and Z each represents the non-metalheat Ethylenedi-p-toluenesulfonate 3,3-ethylenetl iacyanine p-toluenesulfonate Thecyanine arylsulfonates are advantageously converted to the moreinsoluble cyanine iodides to facilitate isolation from the reactionmixture, by treatment with sodium or potassium iodide. The cyaninebromides and perchlorates can be similarly obtained.

The heterocyclic base derivative of methane is advantageously heatedwith the alkylene aryl sulfonate at from 150 to 200 C., although higheror lower temperatures can be used. The acidbinding agent employed toconvert the hydrosalt to the N,N-alky1ene cyanine salt is advantageouslya strong organic base, such as a trialkylamine, a dialkylamine, aN-alkylpiperidine, etc., although sodium carbonate, ammonia or otheracid-binding agents can be used. As alkylene arylsulfonates, alkylenep-toluenesulfonates are advantageously employed, although alkylenebenzenesulfonates and other alkylene arylsulfonates can be employed.

The following examples will serve to illustrate our new dyes and themanner of obtaining them.

Example 1.3,3-ethylenethiacyanine iodide orig-021K 8.4 g. (1 mol.) ofdi-2-benzothiazolylmethane and 11.1 g. (1 mol.) of ethylenedi-p-toluenesulfonate were heated together for 5 hours, at 170 C. Theresulting solid yellow product was cooled and crushed under 25 cc. ofacetone. The crushed yellow product was filtered off with suction andwashed on the filter with acetone. The hydrop-toluenesulfonate thusobtained was suspended in 50 cc. of hot methyl alcohol and an excess oftriethylamine was added to the suspension. The yellow solid dissolved atonce, giving a clear yellow solution. An excess of sodium iodide,dissolved in cc. of hot methyl alcohol, was added to the yellow solutionto convert the 3,3'-ethylenecyanine p-toluenesulfonate to the moreinsoluble 3,3-ethylenecyanine iodide. The resulting mixture was chilledto 0 C., filtered with suction, and the cyanine iodide washed 0n thefilter with methyl alcohol and with water. The yield of yellow crystalsof 3,3'-ethylenethiacyanine iodide was 6 g. (46%). Afterrecrystallization from methyl alcohol (140 cc. per gram of cyanineiodide), the product melted above 330 C. The yield afterrecrystallization was 38%.

Example 2.-1,1'-ethylene-2,2'-cyanine iodide 5.4 g. (1 mol.) ofdi-2-quino1ylmethane and 7.4 g. (1 mol.) of ethylenedi-p-toluenesulfonate were heated together at 160 C. for 16 hours. Theviscous red product was cooled, washed by decantation with two cc.portions of acetone, and the residue dissolved in 30.00. of hot methylalcohol. To the resulting solution of the hydrop-toluenesulfonate of thedye was added an excess of triethylamine. To the resulting mixture wasthen added an excess of sodium iodide dissolved in 20 cc. of hot methylalcohol to convert the 1,1'-ethylene-2,2'-cyanine p-toluenesulfonate tothe more insoluble 1,1-ethylene-2,2-cyanine iodide. The resultingmixture was chilled to 0 C., and the cyanine iodide filtered off withsuction. It was washed on the filter with acetone and water and dried inthe air. The yield of minute green crystals was 1.4 g. (16%). Afterrecrystallization from methyl alcohol (30 cc. per gram of crystals), thecyanine iodide was obtained as red needles, having a green reflex andmelting above 330 C. The recrystallized yield was 5 per cent.

Example 3.--3,3'-ethyleneo:racyanme zodide 2.6 g. (1 mol.) ofdi-2-benzoxazolylmethane and 3.7 g. (1 mol.) of ethylenedi-p-toluenesulfonate were heated together at 230 C. for 10 minutes. Theresulting viscous greenish product was cooled, washed by decantationwith 15 cc. of acetone and dissolved in 20 cc. of hot methyl alcohol. Tothe resulting solution containing the hydro-p-toluenesulfonate wereadded 2 cc. of triethylamine. The 3,3-ethyleneoxacyaninep-toluenesulfonate was converted to the more insoluble3,3'-ethyleneoxacyanine iodide by adding to the mixture an excess ofsodium iodide dissolved in hot methyl alcohol. The mixture was thenchilled to 0 C., the cyanine iodide filtered 011 with suction, washed onthe filter with water and then with acetone. After recrystallizationfrom methyl alcohol, the product consisted of a mixture of pale yellowneedles and colorless crystals. The colorless material was removed byextraction with three 25 cc. portions of acetone. The remaining yellowcrystals were then recrystallized from methyl alcohol cc. per gram ofcrystals). The recrystallized yield was 0.3 g. (8%). The cyanine iodidemelted above 325 C.

In a manner similar to that illustrated in the foregoing examples otherN,N'-alkylenecyanine dyes can be prepared from heterocyclic basederivatives of methane, e. g. di-2-benzoselenazolylmethane, di-2-(4-methyl-thiazolyl) -methane, di- 2- (4-phenylthiazolyl) -methane,di-2- (5-methylbenzoxazolyl) -methane,2-benzothiazolyl-2-quinolylmethane or2-benzoxazolyl-2-benzothiazo1ylmethane. Di-Z-quinolylmethane isdescribed by Scheibe and Fischer, supra. Di-Z-benzothiazolylmethane canbe prepared by condensing o-aminophenyl mercaptan with ethylmalonateaccording to the method of Mills, J. Chem. Soc. 121, 455 (1922).Di-2-benzoxazolylmethane and di-2- benzoselenazolylmethane can also beprepared according to the method of Mills, using o-aminophenol oro-aminoselenophenol instead of oaminophenyl mercaptan.Di-2-(4-methylthiazolyl) -methane and di-2- (4-phenylthiazolyl) methanecan be prepared as described by H. Lehr et al., Helv. chim. Acta 27, 970(1944). Di-2-(5- methylbenzoxazolyl)-methane and2-benzoxazolyl-2-benzothiazolyl-methane are described in United StatesPatent 2,323,503, dated July 6, 1943, and any of the heterocyclic basederivatives set forth in that patent can be employed in practicing ourinvention. The following example shows the preparation ofdi-Z-benzoxazolylmethane.

Example 4.Di-2-benzoxazolylmethane 96.3 grams (2 mols.) of o-aminophenoland 71.0

grams (1 mol.) of ethyl ma-l'on'ate' were boiled gently under reflux for30 minutes. A stream of CO2 gaswa's passed through the apparatus duringthe reaction and steam was passed through the condenser to facilitatethe escape of the ethyl alcohol formed in the condensation. The reactionmixture was cooled and extracted with 1200 cc. hot ligroin and dried.The yield of pinkish crystals melting at 96 to 98 C. was 33.3 grams, 30per cent.

2-benzothiazolyl-2-quinolylmethane can prepared by condensing2-chlorobenzothiazole with quinaldine. The following example illustratesthe preparation:

Example 4a.2-benzothiazolyl-Z-quinolfllmethane 85 g. (1 mol.) of2-chlorobenzothiazole and 143 g. (2 :mols.) of quinaldine were boiledtogether under reflux for 20 minutes. The resulting orange mixture wascooled, made alkaline with per cent sodium hydroxide solution and excessquinal'dine removed by steam distillation. The residue from thedistillation was washed by decantation with water, and the stickyresidue was extracted with 1600 cc. of hot ligroin. (An insolubleresidue contains a tri-nuclear base, di-2-henzothiazolyl-2-quinolylmethane.) The ligroin solution was chilled to0 C., the orange crystals filtered off with suction, Washed on thefilter with ligroin and. dried. The yield was 33.0 g., 24 per cent.After recrystallization from ligroin, the product was obtained as orangecrystals melting at 82 to 83 C. The. yield of purified material was 19per cent.

N,N'-alkylenecyanine dyes in which the alkylene group contains from 2 to3 carbon atoms can also be prepared, we have found, by heating a N-bromoalkylcyanine base of the following general formula:

wherein n represents a positive integer of from 2 to '3, and Z and Zeach represents the nonmetallic atoms necessary to complete aheterocycl-ic nucleons containing from 5 to b atoms in the heterccyclicring. The process can be illus trated for 3,3' ethylenethiacyaninebromide as The heating is advantageously carried out at from 150 to 220C. The resulting N,N'-alkylenecyanine bromide can be converted into themore insoluble iodide by treatment of an alcoholic solution thereof withan alcoholic solution of an alkali metal iodide. Using an alkali metalperchlorate, the N,N'aikylene cyanine perchlorates can be obtained. TheN.1 I-alkylene cyanine bromides and iodidescan be-converted into thechlorides by treatment with silver chloride in a 6 phenol according tothe process describedin United States Patent 2,245,249, datedJimel'O,1941.

The starting N-bromoaikylcyanine base-can be prepared by condensing aN-hydroxyalkyl- 'cyanine base with phosphorous tribromide. TheN-hydroxyalkylcyanine bases can be obtained by condensing acycl'ammon-ium ,(nhydroxyethyl or *y-hfYdIOXYlOIOpyi quaternary saltcontaining a reactive methyl group in the a-positi'on with aheterocyclic nitrogen base containing, in the upcsition, a thioethergroup, e. g. an alkylt'hio group or an arylthio group, in thepresence-of an acid-binding agent, "e. g. a tertiary organic amine, suchas pyridine, a tria'lkylamin'e, or N-methyl piperidine, or an alkalimetal carbonate, such as potassium or sodium carbonate. The startingcyanine base canv also be prepared by reacting with ethylene bromohydrinor propylene-1,3 bromohydrin upon a base of the following "formula:

wherein Z and Z each represents the non-metallic atoms necessary tocomplete a heterocycl i'c nucleus containing from -5 to 6 atoms" intheheterocyclic ring, and then reacting upon the resulting hydrobromidewith an acid-binding agent to split out the elements of hydrogenbromide. The acid-binding agent employed in this case is advantageouslyammonia, although other organic bases, such as those given immediatelyabove can also be employed, as can alkali metal carbonates.

Typical heterocyclic nuclei wherein Z and Z' in the above generalformulas represent the non-metallic atoms necessary to complete aheterocycl-ic nucleus containing from 5 to 6 atoms in the heterocyclicring include those selected from the group consisting of those of thethiazole series (e. g. thiazole, l-methylthiazole, 5-methylthiazole,4-phenylthiazole, fiphenylthiazole, 4,5 dimethy-lthi-azole, 4,5diphenylthiazole, -(2-thienylthiazole, etc.) those of the benzothiazoleseries (e. g. benzothiazole, 4- chlorobenzothiazole,5-chlorobenzothi'a'zole, 6- chlorobenzothiazole, 7 chlorobenzothiazole,4- methylben zothiazole, 5-methylbenzothiazole, 6- methylbenzothiazole,5-bromobenzothiazole, 6- bromobenzothiazole, 4 phenylbenzothiazole, 5-phenylbenzothiazole, 4 methoxybenzothiazole. 5 methoxybenzothiazole, 6methoxybenzothiazole, 5 idobenzothiaznle, fi-iodobenzothiazole, 4ethoxybenzothiazole, 5-ethoxybenzothiazole, tetrahydrobenzothi-azole,5.6 'dimethoxybenzothiazole, 5,6 dioxymethylenebenzothiazole, 5-hydroxybenzothiazole, 6 hydroxybenzothiazole, etc), those of thenaphthothiazole series (e.- g. a-naphthothiazole, p-naphthothiazol'e, 5methoxy finaphthothiazole, 5-ethoXy-/3-naphth'othiazole, '7 methoxy anaphthothiazole, 8':- n'iethoxy-a naphthothiazole, etc). those of thethionaphtheno-7,6', l,5 thiazole series. (e. gr 4',-'methoxythionaphtheno 7','6 '-,4,5-thiazole; etc), those of the oxazoleseries (e. .g'. 'e methyloxa'zol'e, 5-methylo'xazoie, l-phenyloxazol'e,4-,5-dipheny1- ox'azole, i-ethyloxazole, 4 ,5-dimethyloxazole, 5--phenyloxazole, etc), those of the benzoxa'z'ode series (e. g.ben-Zoxazole, 5-chlorobenzox'azole, 5-- phenylbenzoxazole, 5methylb'enzoxaz'ole, 6- methylben'zoxazole, 5,6 dimethylbenzoxaiole,4,G-dimethyIbenZoxaZole, 5-methoxybenzoxa'zole, 6-methoxybenzoxazole,5-etlroxybenzoxazole, 6-

e as the iodide.

chlorobenzoxazole, -hydroxybenzoxazole, 6-hydroxyzenboxazole, etc.),those of the naphthoxazole series (e. g. a-naphthoxazole,,B-naphthoxazole, etc.), those of the selenazole series (e. g.4-methylselenazole, l-phenylselenazole, etc.), those of thebenzoselenazole series (e. g. benzoselenazole, 5 chlorobenzoselenazole,5- methoxybenzoselenazole, 5-hydroxybenzoselenazole,tetrahydrobenzoselenazole, etc.), those of the naphthoselenazole series(6. g. e-naphthoselenazole, B-naphthoselenazole, etc.), those of thethiazoline series (e. g. thiazoline, 4-methylthiazoline, etc), etc. Z,in addition, can represent the non-metallic atoms necessary to completea heterocyclic nucleus selected from those of the 2-quinoline series (e.g. quinoline, 3- methylquinoline, 5 methylquinoline, 7-methylquinoline,8-methylquinoline, 6-chloroquinoline, 8 chloroquinoline, 6methoxyquinoline, 6- ethoxyquinoline, 6 hydroxyquinoline, 8hydroxyquinoline, etc.), those of the 4-quinoline series (e. g.quinollne, S-methoxyquinoline, 7- methylquinoline, 8-methylquinoline,etc), those of the l-isoquinoline series (e. g. isoquinoline,3,4-dihydroisoquinoline, etc.), those of the 3- isoquinoline series (e.g. isoquinoline, etc.) those of the 3,3-dialkylindolenine series (e. g.3,3-dimethylindolenina, 3,3,5 trimethylindolenine,3,3,7-trimethy1indolenine, etc.), those of the 2- pyridine series (e. g.pyridine, S-methylpyridine, 4-methylpyridine, 5-methylpyridine,6-methy1- pyridine, 3,4-dimethylpyridine, 3,5-dimethylpyridine,3,6-dimethylpyridine, 4,5-dimethylpyridine, 4,6-dimethylpyridine,l-chloropyridine, 5-chloropyridine, S-chloropyridine, 3-hydroxypyridine,4-hydroxypyridine, 5-hydroxypyridine, '6-hydroxypyridine,3-phenylpyridine, -phenylpyridine, G-phenylpyridine, etc.), those of the4- pyridine series (e. g. Z-methylpyridine, 3-methylpyridine,z-chloropyridine, 3-chloropyridine, 2,3- .dimethylpyridine,2,5-dimethylpyridine, 2,6-dimethylpridine, 2-hydroxypyridine,3-hydroxypyridine, etc.), etc.

The following examples will serve to illustrate the manner of obtainingN,N-alkylenecyanine dyes from N-bromoalkylcyanine dyes:

Example 5.3,3-ethyZenethiacyanine iodide C=CH (when, I

2 g. (1 mol.) of 2-(3- 3-bromoethyl-2(3)- benzothiabolylidene)methylbenzothiazole were heated at 170 C. for 4 hours. The resultingyellow product (3,3'-ethylenethiaoyanine bromide) was cooled anddissolved in 20 cc. of hot methyl alcohol. To the hot methyl alcoholsolution was added a solution of sodium iodide in methyl alcohol'toprecipitate the 3,3-ethylenethiacyanine The resulting mixture waschilled to 0 C.; and the cyanine iodide filtered off with suctionand'washed on the filter with 10 cc. of acetone, followed by 10 cc. ofwater. The cyanine iodide was then dried in the air. 1.9 g. (85% yield)of the cyanine iodide was obtained asyellow crystals. Afterrecrystallization from methyl alcohol (140 cc. per gram of cyanineiodide); the cyanine iodide melted above 330 C. The yield ofrecrystallized product was 1.4 g. -(63%). The cyanine iodidergave ayellow solu- 8 tion in methyl alcohol, having a strong bluefluorescence.

The 2 (3-p-bromoethyl-2(3)-benzothiazolylidene) methylbenzothiazoleemployed above, was prepared as follows:

3.9 g. (1 mol) of 2-(3-B-hydroxyethyl-2(3)- benzothiazolylidene)methylbenzothiazole and 10 cc. of phosphorus tribromide were heatedtogether on a steam bath for one hour. A yellow solution formed Whichset to a solid mass of yellow crystals after 10 minutes heating. Thereaction mass was cooled, broken up, and poured onto ice and madealkaline with 30 per cent ammonium hydroxide. The yellow crystals of thefi-bromoethyl compound were then filtered ofi, washed on the filter withwater, and dried in the air. The yield was 3.7 g. (79%), and thecrystals melted initially at to C. As the temperature of the meltingpoint bath was raised higher, the product resolidified and did notremelt at 320 C. The product appeared to rearrange upon attemptedrecrystallization from acetone giving a substance which melted above 320C. Accordingly, the original air-dried product was used without furthertreatment.

The 2 (3-fi-hydroXyethyl-2 (3) -benzothiazolylidene) methylbenzothiazolI en ers-0H employed above was prepared as follows:

14.1 g. (1 mol.) of di-2-benzothiazolylmethane (prepared by the methodof Mills, J. Chem. Soc. 121, 455, 1922) and 6.25 g. (1 mol.) of ethylenebromohydrin were heated together at C. for 16 hours. The resultingyellow solid mass was crushed under 50 cc. of cold acetone, filteredwith suction, washed on the filter with 25 cc. of acetone and dried inthe air. The yield of yellow crystals was 19.8 g. (97%) which melted at256 to 258 C. with decomposition. The bromide Bl CH2CHg-OH thus obtainedwas suspended in 50 cc. of methyl alcohol and the resulting suspensionwas made alkaline with 25 cc. of 30 per cent ammonium hydroxide. Thesolid bromide dissolved at once, giving a yellow solution from which thefree base separated as yellow crystals upon stirring. The mixture waschilled at 0 C., filtered with suction, washed on the filter with 25 cc.of methyl alcohol and dried in the air. After recrystallization frommethyl alcohol (100 cc. per gram of base), the base was obtained asyellow needles, melting with decomposition at to 187 C. The yield was11.9 g. (73%).

am e, ,'.3-.ethyle thia-2ermine io e 7.6 g. (1 mol.) of2-(3-/3-bromoethyl-2(3)- benzothiazolylidene)methylquinoline were heatedat 170 C. for three hours. The red solid product was recrystallizedseveral times from MeOH (200 cc. per gram). The yield of purified dyewas 2.4 g., 28%. The dye melted at 320-25 C. with decomposition.

The 2-(3'fl-bromoethyl 2(3) benzothiazolylidene) -methylquinolineemployed above was preared as follows:

10.7 g. (1 mol.) of 2-(3-B-1ydroxyethyl-2(3)-benzothiazolylidene)methylquinoline and cc. of PBr-s were boiledtogether under reflux for five minutes. The product was cooled, stirredwith ice and water, filtered with suction and washed on the filter withwater and acetone. The red crystals were then suspended in 50 cc. MeOHand the mixture made alkaline with NazCOa. The sticky brown product wasfiltered off, washed with MeOH and recrystallized from lvleOI-I (450 cc.per gram). The yield of purified product was 8.5 g, 67%. The product wasobtained as orange needles melting at 147-8 C.

The 2-(3-fl-hydroxyethyl-2(3)-benzothiazoly1- idene) -methylquinolineemployed above was prepared as follows:

31.2 g. (1 mol.) of 2-methylbenzothiazole-B'- hydroxy ethobromide and25.0 g. (1 mol.+25% excess) of 2-methylmercaptoquino-line were boiledunder refiux for fifteen minutes. The red solid product was cooled,washed by decantation with 200 cc. cold acetone and recrystallized from3000 cc. MeOH. The yield of red crystals melting at 27'78 C. was 15.4g., 34%. The hydrobrornide thus obtained was then suspended in 100 cc.abs.

EtOH and 5 cc. triethylamine added. The mixture Was chilled, dilutedwith 1000 cc. of water and the free base filtered off. The yield oforange crystals which melted at 1434 C. was 11.0 g., 30%. r

In a manner similar to that illustrated in the foregoing Examples 5 and6, 1,3-ethyleneselena- 2-cyanine iodide, 3,3'-ethyleneselenathiacyanineiodide, 3,3-propylenethiacyanine iodide and 3,3- ethyleneselenacyanineiodide can be prepared.

Example 7.3,3-propylenethiacyanine bromide s s \C=CH-C\/\ 1.0 g. (1mol.) of 2-(3-' -bromopropyl-2(3)- benzothiazolylidenemethylbenzothiazole w a s heated strongly over a flame until the productsolidified (about 30 seconds). The mixture was cooled, stirred with cc.of acetone, chilled to 0 C. and filtered with suction. The yield ofyellow crystals was 0.5 g. (50%) After recrystallization from methylalcohol (100 cc./g. of dye), the product was obtained as a yellowpowdermelting with decomposition at 300 to 003 C. The yield of pure dyewas 0.4 g. (40%). The dye was found to be a moderately strongsensitizer, extending the sensitivity of a gelatino-silver 10 halideemulsion to 470 mp with no definite maximum.

The 2- (3--y-bromopropyl-2-(3) -benzothiazolylidene)methylbenzothiazoleemployed above was prepared as follows:

1.5 g. 1 mol.) of 2-(-3- -hydroxypropyl-2(3)benzothiazolyl-idene)methylbenzothiazole and 5 cc. of PBI3 were heatedto boiling in a test tube. A yellow solid separated at once. Thereaction mixture was colled, made alkaline with cold dilute NazCOssolution, and the product filtered with suction, washed with water anddried. The yield of yellow crystals was 1.3 g. (73%). Afterrecrystallization from MeOI-I (167 cc./g. of product) the'product meltedat 134136 0., resolidified as the temperature was raised further andmelted again at"292-2 93-- C.

The 2-(3- -hydroxypropy1-2 (-3) benzothiazolylidene) methylbenzothiazoleemployed above was prepared as follows:

5.0 g. (1 mol.) of di-2benzothiazolylmethane and 2 .5 g. (1 mol.) oftrimethylenebromohydrin were heated together on a steam bath for 16hours. The yellow solid product was crushed under 25 cc. of acetone,chilled to 0 C. and filtered with suction. The solid was washed on thefilter with 10 cc. of fresh acetone and dried. The yield of yellowcrystals was 2.6 g. (35%). The bromide was then suspended in 25 cc. ofMeOH and made alkaline with NHiOH while stirring. The yellow base wasfiltered 01f, washed on the filter with water and dried. The yield was1.8 g. (31%) of product melting at 121-122 C.

In a manner similar to that illustrated in the foregoing Examples 5, 6and '7', 1',3'-ethylene- Selena-2' -cyanine iodide, 3,3-ethyleneselenathiaoyanine, 3,3-propylenethiacyanine iodide and3,3-ethyleneselenacyanine iodide can be prepared.

The symmetrical N,N'-alkylenecyanine dyes, prepared from thebis-(heterocyclyl)methanes wherein Z and Z of the above general formulaare identicaL'containing a simple thiazole nucleus (e. g.4-methylthiazole, 4-phenylthiazole, etc), a benzothiazole nucleus, abenzoxazole nucleus or a benzoselenazole nucleus are new. Theunsymmetrical N,N'-alkylenecyanine dyes prepared from thebis(heterocyclyl)methanes wherein Z and Z of the above general formulaare different from one another are also new.

The N,N-a kylenecyanine dyes obtainable by our process sensitizephotographic silver halide emulsions when incorporated therein. Thefollowing table shows the sensitizing action of the N,N'-alkylenecyaninedyes of Examples 1 to 6.

In the preparation of photographic emulsions containing our new dyes, itis only necessary to disperse the dyes in the emulsions. The methods ofincorporating dyes in emulsions are simple and well known to thoseskilled in the art. It is convenient to add the dyes from solutions inappropriate solvents. Methanol has proven satisfactory as a solvent forour new dyes. Ethyl alcohol 11 or acetone may also be employed where thesolubility of the dyes in methanol is lower than desired.

Sensitization by means of our new dyes is, of course, directed primarilyto the ordinarily employed gelatino silver halide developing outemulsions. The dyes are advantageously incorporated in the washed,finished emulsions and should, of course, be uniformly distributedthroughout the emulsions.

The concentration of our new dyes in the emulsion can vary widely, i. e.from about to about 100 mgs. per liter of fiowable emulsion. Theconcentration of the dye will vary according to the type oflight-sensitive material in the emulsion and according to the effectsdesired. The suit-- able and most economical concentration for any givenemulsion will be apparent to those skilled in the art upon making theordinary tests and observations customarily used in the art of emulsionmaking.

To prepare a gelatino-silver-halide emulsion sensitized with one of ournew dyes, the following procedure is satisfactory: A quantity of the dyeis dissolved in methyl alcohol or other suitable solvent and a volume ofthis solution (which may be diluted with water) containing from 5 to 100mgs. of dye is slowly added to about 1000 cc. of agelatino-silver-halide emulsion, with stirring. Stirring is continueduntil the dye is uniformly distributed throughout the emulsion. Withmost of our new dyes, to 20 mgs. of dye per liter of emulsion sufiicesto produce the maximum sensitizing efiect with the ordinarygelatino-silverbromide (including bromiodide) emulsions. With fine-grainemulsions, which includes most of the ordinarily employedgelatino-silver-chloride emulsions, somewhat larger concentrations ofdye may be necessary to secure the optimum sensitizing effect.

The above statements are only illustrative and are not to be understoodas limiting our invention in any sense, as it will be apparent that ournew dyes can be incorporated by other methods in many of thephotographic silver halide emulsions customarily employed in the art.For instance, the dyes may be incorporated by bathing a plate or filmupon which an emulsion has been coated, in the solution of the dye, inan appropriate solvent. Bathing methods, however, are not to bepreferred ordinarily.

Our new dyes give rise to two extreme resonance configurations as doN,N-dialky1cyanine dyes. For instance in the case of1.3-ethylenethia-2-cyanine iodide (Example 6, the extreme configurationscan be represented as follows:

(fl il) N The term simple thiazole is employed herein to indicate athiazole which does not contain a fused-on aryl nucleus.4-Methylthiazo1e and 4- phenylthiazole are typical simple thiazoles.

12 Benzothiazole, on the other hand, contains a fused-on benzenenucleus.

This application is a division of our application Serial No. 563,086,filed November 11, 1944, now U. S. Patent 2,478,367, dated August 9,1949.

What we claim as our invention and desire secured by Letters Patent ofthe United States is:

1. A process for preparing a N,N-alkylenecyanine dye comprising heatinga N-bromoalkylcyanine base of the following general formula:

wherein Z represents the non-metallic atoms necessary to complete aheterocyclic nucleus of the benzothiazole series.

3. A process for preparing a symmetrical N,N'- alkylenecyanine dyecomprising heating a N- bromoethylcyanine base of the following formula:

4. A process for preparing an asymmetrical N N'-alkylenecyanine dyecomprising heating a N-bromoethylcyanine base of the following generalformula:

wherein Z represents the non-metallic atoms necessary to complete aheterocyclic nucleus of the benzothiazole series and Z represents thenon-metallic atoms necessary to complete a heterocyclic nucleus of thequinoline series.

5. A process for preparing an asymmetrical N,N-alkylenecyanine dyecomprising heating a N-bromoethylcyanine base of the formula:

6. A process for preparing a symmetrical N,N'- alkylenecyanine dyecomprising heating a N- bromopropylcyanine base of the following generalformula:

Br-(CHfia-N c=oH-d=1 I wherein Z represents the non-metallic atomsnecessary to complete a heterocyclic nucleus of the benzothiazoleseries.

7. A process for preparing a symmetrical N,N'- alkylenecyanine dyecomprising heating a N- bromopropylcyanine base of the followingformula:

0 v I N C Hz-CH2CHz-Bl 8. The asymmetrical N,N'-alkylenecyanine dyes ofthe following general formula:

/Z\ ,z'\ I I N- =cH-c- N-X wherein n represents a positive integer offrom 2 to 3, X represents an anion, Z represents the non-metallic atomsnecessary to complete a heterocyclic nucleus selected from the groupconsisting of benzothiazole, benzoxazole and benzoselenazole nuclei andZ is different from Z and represents the non-metallic atoms necessary tocomplete a heterocyclic nucleus selected from the group consisting ofbenzothiazole, benzoxazole, benzoselenazole and quinoline nuclei.

9. The asymmetrical N,N-alyklenecyanine dyes of the following generalformula:

ZL. wherein X represents an anion, n represents a positive integer offrom 2 to 3, Z represents the non-metallic atoms necessary to complete abenzothiazole nucleus and Z represents the nonmetallic atoms necessaryto complete a quinoline nucleus.

10. The asymmetrical N,N-alkylenecyanin dyes of the following formula:

IIZ\\ I 1 I C=CH-C=N-I CHPCHZ wherein Z represents the non-metallicatoms necessary to complete a benzothiazole nucleus and Z represents thenon-metallic atoms necessary to complete a quinoline nucleus.

11. The asymmetrical N,N-alkylenecyanine dye of the following generalformula:

GE 3H LESLIE G. S. BROOKER. ROBERT H. SPRAGUE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,478,367 Brooker Aug. 9, 19492,479,152 Brooker Aug. 16, 1949 OTHER REFERENCES Scheibe, Berichte, V01.59, pp. 502-508, 1926.

hs'droxyethyl read 2-(3-fl-hydr0wyethg Z; column 10,1 ine 1-0, forcolled, read foo'oled; column 14, line 12, strike out the WOflY afterfollowing in line 2, same column;

and that the said Letters Patent should be read as corrected above, sothat Certificate of Correction Patent No. 2,541,400 February 13, 1951LESLIE G. S. BROOKER ET AL.

It is hereby certified that error appears in the'printed specificationof the above numbered patent requiring correction as follows:

Column 4, line 8, for 30 cc. read 50 00.; column 8, line 34:, for 2(3-B-general and insert the same V the same may conform to the record of thecase in the Patent Ofiice.

Signed and sealed this 15th day of May, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

8. THE ASYMMETRICAL N,N''-ALKYLENECYANINE DYES OF THE FOLLOWING GENERALFORMULA: